I was delighted to see these nanohana (菜の花, or rapeseed) flowers in a subway display promoting rail trips to Izu, a subtropical peninsula a few hours from Tokyo. Rapeseed can be eaten like brocoli, used to make canola oil, or planted as a winter cover crop to improve soil quality. It is clever to promote rail trips to the countryside by bringing a bit of nature into the subterranean tunnels of heavily trafficked Shibuya station.